| Message ID | 20170922061008.14723-4-fw@strlen.de |
|---|---|
| State | Rejected, archived |
| Delegated to: | David Miller |
| Headers | show |
| Series | rtnetlink: preparation patches for further rtnl lock pushdown/removal | expand |
On 9/22/17 12:10 AM, Florian Westphal wrote: > We can use rcu here to make this safe even if we would not hold rtnl: > qdisc_destroy uses call_rcu to free the Qdisc struct. > > Signed-off-by: Florian Westphal <fw@strlen.de> > --- > net/core/rtnetlink.c | 16 ++++++++++++++-- > 1 file changed, 14 insertions(+), 2 deletions(-) Reviewed-by: David Ahern <dsahern@gmail.com>
On Fri, 2017-09-22 at 08:10 +0200, Florian Westphal wrote: > We can use rcu here to make this safe even if we would not hold rtnl: > qdisc_destroy uses call_rcu to free the Qdisc struct. Where do you see call_rcu() called from qdisc_destroy() ? You missed this commit I guess 752fbcc33405d6f8249465e4b2c4e420091bb825 ("net_sched: no need to free qdisc in RCU callback")
Eric Dumazet <eric.dumazet@gmail.com> wrote: > On Fri, 2017-09-22 at 08:10 +0200, Florian Westphal wrote: > > We can use rcu here to make this safe even if we would not hold rtnl: > > qdisc_destroy uses call_rcu to free the Qdisc struct. > > > Where do you see call_rcu() called from qdisc_destroy() ? > > You missed this commit I guess > > 752fbcc33405d6f8249465e4b2c4e420091bb825 > ("net_sched: no need to free qdisc in RCU callback") Indeed, I did, patch dropped, thanks for the heads-up.
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c index c801212ee40e..ad3f27da37a8 100644 --- a/net/core/rtnetlink.c +++ b/net/core/rtnetlink.c @@ -1332,6 +1332,19 @@ static int nla_put_iflink(struct sk_buff *skb, const struct net_device *dev) return nla_put_u32(skb, IFLA_LINK, ifindex); } +static int nla_put_qdisc(struct sk_buff *skb, struct net_device *dev) +{ + struct Qdisc *q; + int ret = 0; + + rcu_read_lock(); + q = READ_ONCE(dev->qdisc); + if (q) + ret = nla_put_string(skb, IFLA_QDISC, q->ops->id); + rcu_read_unlock(); + return ret; +} + static int rtnl_fill_ifinfo(struct sk_buff *skb, struct net_device *dev, int type, u32 pid, u32 seq, u32 change, unsigned int flags, u32 ext_filter_mask, @@ -1372,8 +1385,7 @@ static int rtnl_fill_ifinfo(struct sk_buff *skb, struct net_device *dev, nla_put_iflink(skb, dev) || put_master_ifindex(skb, dev) || nla_put_u8(skb, IFLA_CARRIER, netif_carrier_ok(dev)) || - (dev->qdisc && - nla_put_string(skb, IFLA_QDISC, dev->qdisc->ops->id)) || + nla_put_qdisc(skb, dev) || (dev->ifalias && nla_put_string(skb, IFLA_IFALIAS, dev->ifalias)) || nla_put_u32(skb, IFLA_CARRIER_CHANGES,
We can use rcu here to make this safe even if we would not hold rtnl: qdisc_destroy uses call_rcu to free the Qdisc struct. Signed-off-by: Florian Westphal <fw@strlen.de> --- net/core/rtnetlink.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-)